Referring to FIG. 1, a conventional power amplifier device includes three Wilkinson dividers 11-13, six power amplifiers 21-26, and three Wilkinson combiners 31˜33. Each of the power amplifiers 21-26 has a power gain of A.
The Wilkinson divider 11 divides an input signal with a power of Pi into first and second signals, each with a power of Pi/2. Each of the power amplifiers 21, 22 amplifies a respective one of the first and second signals by the power gain to obtain a respective one of first and second amplification signals, which has a power of (Pi/2)×A. The Wilkinson divider 12 divides the first amplification signal into third and fourth signals, each with a power of (Pi/4)×A. The Wilkinson divider 13 divides the second amplification signal into fifth and sixth signals, each with a power of (Pi/4)×A. Each of the power amplifiers 23-26 amplifies a respective one of the third to sixth signals by the power gain to obtain a respective one of third, fourth, fifth and sixth amplification signals, which has a power of (Pi/4)×A2. The Wilkinson combiner 31 combines the third and fourth amplification signals to obtain a seventh signal with a power of (Pi/2)×A2. The Wilkinson combiner 32 combines the fifth and sixth amplification signals to obtain an eighth signal with a power of (Pi/2)×A2. The Wilkinson combiner 33 combines the seventh and eighth signals to obtain an output signal with a power of Pi×A2.
However, since three Wilkinson dividers 11-13 are required to divide the input signal into four signals, and since three Wilkinson combiners 31-33 are required to combine four signals into the output signal, the conventional power amplifier device disadvantageously has a relatively large area and a relatively high cost.